Adamantane is a stable, highly symmetrical compound in which four cyclohexane rings are condensed to form a cage-like structure. It is known that adamantane, which has such a specific adamantane skeleton and which shows peculiar functions, is useful as a lubricant or as a raw material for agricultural and medical materials and highly functional industrial materials.
As a method for producing adamantane, a process is generally adopted in which trimethylenenorbornane obtained by hydrogenating dicyclopentadiene is isomerized.
In such an isomerization reaction, aluminum chloride is generally used as a catalyst.
The yield of adamantane produced by using aluminum chloride as a catalyst is about 50% by mass (for example, Patent Documents 1 and 2). In this case, the catalyst must be used in a large amount and further cannot be reused because it forms complexes with heavy components during the reaction.
Therefore, the known method produces a large amount of waste aluminum, disposal of which causes problems of environmental pollution.
In addition, since the use of aluminum chloride causes coloring of the adamantane product, it is necessary to conduct a recrystallization step and a decoloring step using, for example, active carbon. Thus, a problem is caused that post treatments become inevitably troublesome.
There is also known a solid catalyst which contains an active metal such as platinum, rhenium, nickel or cobalt carried on a cation-exchanged zeolite by an impregnation process (for example, Patent Document 3).
A process for producing adamantane using the above solid catalyst in which an active metal such as platinum, rhenium, nickel or cobalt is carried on a cation-exchanged zeolite by an impregnation process can solve the above problems caused in the case where aluminum chloride catalyst is used.    Patent Document 1: JP-A-Shou-50-71663    Patent Document 2: JP-A-2000-143556    Patent Document 3: JP-B-Shou-52-2909
The above-described conventional methods using aluminum chloride catalyst or a solid catalyst, however, have a problem that the production of adamantane requires unavoidably a high cost because trimethylenenorbornane used as a starting material should be obtained by hydrogenating dicyclopentadiene which is expensive.